Droplet actuators are used to conduct a wide variety of droplet operations. A droplet actuator typically includes a substrate associated with electrodes configured for conducting droplet operations on a droplet operations surface thereof and may also include a second substrate arranged in a generally parallel fashion in relation to the droplet operations surface to form a gap in which droplet operations are effected. The gap is typically filled with a filler fluid that is immiscible with the fluid that is to be subjected to droplet operations on the droplet actuator. In some applications, it is useful to detect absorbance of a droplet or other fluid, and in some cases, the fluid is located on a droplet actuator. There is a need in the art for improved droplet actuator devices and methods for this purpose.